Windmill structure for use in wind power apparatus

ABSTRACT

In order to provide a windmill structure capable of preventing a blade from damage based on a strong wind, the windmill structure is for use in a wind power apparatus in which a dynamo-electric generator is driven by a main shaft to which a rotation of the windmill is transmitted. The windmill comprising at least one blade which extends in a radial direction from a blade supporting portion of a main shaft tip in relation to the main shaft. The windmill structure comprises the blade comprising a fixing portion supported on the blade supporting portion and extending to a radial direction, and a moving portion connected to an upper end of the fixing portion. The moving portion is capable of projecting and retreating from the fixing portion to the radial direction. The windmill structure further comprises control means for changing the projection length of the moving portion in accordance with a wind speed.

BACKGROUND OF THE INVENTION

The present invention relates to a windmill structure having a pluralityof blades in a wind power apparatus.

A wind power apparatus is known which rotates a windmill having aplurality of propeller shaped blades, to generate electric power. In thewind power apparatus, the windmill and a dynamo-electric generator areinstalled at an upper end of supporting post. For example, the windmillhas three blades which extend from a main shaft to a radial directionand which are positioned with a regular angle around the main shaft.

The wind power apparatus usually has sensors such as an anemoscope andan anemometer. In response to information obtained by the anemoscope,the windmill is directed to a direction at which wind blows. Thewindmill rotates by the wind which blows from the front. A plurality ofpublications such as patent publications 1 and 2 is well known in theart in concern to the wind power apparatus having such a windmill.

-   -   (Patent Publication 1)    -   Japanese Unexamined Patent publication Tokkai Hei 8-128385    -   (Patent Publication 2)    -   Japanese Unexamined Patent publication Tokkai 2000-87841

As described above, the windmill may be damaged by a strong windexceeding the endurance of the windmill, in the windmill having theblades which extend from the main shaft to a radial direction. Althoughit is desired that the area for receiving the wind is large in each ofthe blades from wind power efficiency, the endurance decreases inrelation to the strong wind in case where each of the blades has a largearea for receiving the wind. Therefore, each of the blades is narrowedin order to endure the strong wind. In addition, each of the blades hasa large length in order to enlarge the receiving area of wind.

Each of the patent publications 1 and 2 discloses a structure ofcontrolling an effective area for receiving the wind by changing anangle in relation the wind in each of the blades for provision of strongwind, in order to preventing each of the blades from damage. Moreparticularly, the surface of the blade is controlled to be parallel tothe direction of the wind, in order to make the resistance be zero inrelation to the wind.

By the way, each of the blades has no plane in the windmill and istwisted into a spiral shape which is directed from a base portion to atip portion such as a propeller. In order to obtaining a rotating force,namely, in order to obtain a high power generating efficiency, thespiral shape is favorable. However, it is impossible to make the entiresurface of the blade be parallel to the wind even if the attachmentangle of the blade having the spiral shape is changed in everydirection. In the blade having the surface of spiral shape, any portionof the blade always receives the resistance of the wind. The blade maybe damaged in accordance with a wind pressure which is not less than theendurance of the blade.

SUMMARY OF THE INVENTION

In order to dissolve the above-mentioned problems, it is an object ofthe present invention to provide a windmill structure comprising atleast one blade having a desired spiral surface in order to obtain ahigh power generating efficiency and capable of preventing the bladefrom damage based on a strong wind.

In order to accomplish the above-mentioned object, according to a firstaspect of the present invention, there is provided a windmill structurein which a dynamo-electric generator is driven by a main shaft to whicha rotation of a windmill is transmitted. The windmill comprises at leastone blade which extends in a radial direction from a blade supportingportion of a main shaft tip in relation to the main shaft. The windmillstructure comprises the blade having a fixing portion supported on theblade supporting portion and extending to a radial direction, and amoving portion connected to an upper end of the fixing portion. Themoving portion is capable of projecting and retreating from the fixingportion to the radial direction. The windmill structure furthercomprises control means for changing the projection length of the movingportion in accordance with a wind speed.

According to a second aspect of the present invention, the fixingportion comprises a front plate and a rear plate, a cavity portion beingformed between said front plate and said rear plate. The moving portionis stored in the cavity portion of the fixing portion when the movingportion retreats.

According to a third aspect of the present invention, the control meanscomprises a male screw rod rotatably supported on the blade supportingportion and extending to the radial direction in the cavity portion ofthe fixing portion, a sensor for detecting the wind speed, driving meansfor make the male screw rod rotate in accordance with an output of thesensor, and a female screw plate fixed on the moving portion and screwedinto the male screw rod. The female screw plate moves along the malescrew rod on the basis of the rotation of the male screw rod so that theprojection length of the moving portion is changed in accordance withthe wind speed.

According to a fourth aspect of the present invention, the windmillstructure comprises a bearing mounted on the fixing portion and a railmounted on the moving portion. The rail is fitted into the bearing. Therail moves with the rail being fitted into the bearing when the movingportion projects and retreats.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an outside prospective view for briefly illustrating awindmill structure of a wind power apparatus according to the presentinvention;

FIG. 2A shows a view for viewing a windmill in condition a blade has thelongest length, from axis direction of a main shaft;

FIG. 2B shows a view for viewing a windmill in condition a blade has theshortest length, from axis direction of a main shaft;

FIG. 3A shows a prospective view for illustrating the blade of windmillin condition the blade has the longest length and an expanded view nearthe upper end of fixing portion;

FIG. 3B shows a prospective view for illustrating the blade of windmillin condition the blade has a middle length and an expanded view near thelower end of moving portion;

FIG. 3C shows a prospective view for illustrating the blade of windmillin condition the blade has the shortest length and an expanded view nearthe upper end of fixing portion;

FIG. 4A shows a developed view in condition of cutting off a part, forillustrating a connecting portion between a moving portion and a fixingportion of one blade; and

FIG. 4B shows a sectional view along X-X line of FIG. 4A.

PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 shows an outside prospective view for briefly illustrating awindmill structure of a wind power apparatus according to the presentinvention. A windmill 10 is installed on an upper end of a supportingpost 15 together with a dynamo-electric generator 14. A reference signC1 represents an axis of the supporting post 15. A blade supportingportion 13 is attached to a tip portion of a main shaft 11 (a leftdirection in FIG. 1) for driving the dynamo-electric generator 14,through a main bearing 12. Three blades 20 a, 20 b, and 20 c, whichspirally extend in relation to the main shaft 11, are attached to theblade supporting portion 13 illustrated in FIG. 1 with a regularinterval of angle. A reference sign C2 represents an axis of the mainshaft 11. The axis C2 of the main shaft 11 is controlled so as to bedirected to the wind which blows to the windmill 10 (arrow R1). Therotary control is carried out on the basis of an output signal of ananemoscope which is included in a sensor.

Incidentally, the windmill structure is characterized by the structureof one blade. Therefore, the blades have structures which are similar toone another. The number of blades may be one or may be the pluralnumber. When the blade 20 a and so on rotate together with the bladesupporting portion 13 by the wind, the rotation is transmitted to themain shaft 11 (arrow R2) and the dynamo-electric generator is driven bythe rotation of the main shaft 11. As a result, power generation iscarried out.

The blade 20 a extends to a radial direction along a blade axis C3perpendicular to the axis C2 of the main shaft 11. Inasmuch as the blade20 a has a propeller shape, the blade 20 a has a spirally twistedsurface. The blade 20 a of the present invention is formed by connectingtwo members which are approximately equal in the length to each other.One member is a fixing portion 22 which is fixed to the blade supportingportion 13 and extends to a radial direction. Another member is a movingportion 23 which extends from the upper end 22 a of the fixing portion22 to the radial direction. The fixing portion 22 has a constant length.The moving portion 23 is capable of projecting from the upper end 22 aof the fixing portion 22 and is capable of retreating from the upper end22 a of the fixing portion 22. It is possible to vary the projectionlength. In the condition of the windmill illustrated in FIG. 1, themoving portion 23 is positioned in the condition of most projection.Namely, the blade 20 a and so on have the longest lengths, respectively.

FIG. 2A shows a view for viewing the windmill in condition the blade 20a and so on have the longest lengths, respectively, from axis directionof a main shaft. On the other hand, FIG. 2B shows a view forillustrating the condition that the moving portion 23 retreats to a mostretreat position, namely, FIG. 2B shows a view for viewing a windmill incondition that the blade 20 a and so on have the shortest lengths,respectively, from axis direction of a main shaft. As shown by an arrow,the moving portion 23 retreats and the length of the moving portionbecomes short. Inasmuch as the receiving area of wind becomes small inthe blade, the blade is hardly damaged by the strong wind in comparisonto the condition of the FIG. 2A.

FIG. 3A to 3C show views each of which illustrates a variation of lengthfrom the longest length to the shortest length in the blade 20 a. Eachleft side drawing shows an outside prospective view of the blade 20 a.Each right side drawing shows a briefly expanded view of a circular partof the respective left side drawing.

FIG. 3A shows a view for illustrating the blade 20 a having the longestlength. The moving portion 23 is positioned at the most projectionposition. The surface near the base end portion of the blade 20 aextends along a straight line A which is approximately perpendicular tothe axis C3 of the main shaft 11. The surface near the tip of the blade20 a extends along a straight line B which is twisted in relation to thestraight line A. When viewing the straight lines A and B from thedirection of the blade axis C3, the straight lines A and B looks as ifthe straight lines A and B forms an angle of 40 degrees to 50 degrees.As described above, the blade 20 a is spirally twisted although blade 20a has a width which is approximately equal from the base end portion tothe tip portion.

As will be described hereinafter, a cavity portion is formed in thefixing portion 22. The moving portion is capable of being stored in thecavity portion of the fixing portion 22. Inasmuch as each of the fixingportion 22 and the moving portion has a common spiral surface with aconstant twisted degree, the moving portion moves along the spiral andis stored in the fixing portion 22.

As shown in the right side drawing of FIG. 3A, the lower end 23 a(broken line) of the moving portion 23 is positioned near the upper end22 a of the fixing portion 22 in the condition that the moving portion23 is positioned at the most projection position.

Although a detailed description will be made in FIG. 5 as regards amechanism will be described which is for making the moving portion 23project and retreat, a male screw rod 25, which spirally extends in thecavity portion of the fixing portion 22 along the blade axis C3, isrotatably supported to the blade supporting on the outer surface of themale screw rod 25. The male screw rod 25 is driven so as to rotate inevery direction by a driving means such as a motor which is notillustrated. The driving means such as a motor may be, for example,attached to the blade supporting portion 13. On the other hand, a femalescrew plate 26, which is screwed into the male screw rod 25, is fixed tothe moving portion 23. A screw groove is formed on an inner surface ofthe female screw plate 26. As a result, the female screw plate 26 movesalong the male screw rod 25 when the male screw rod 25 is rotated (arrowR3). The moving portion 23 moves together with the female screw plate26.

FIG. 3B shows a prospective view for illustrating the blade 20 a incondition the blade has a middle length between the longest length andthe shortest length. The moving portion 23 projects in a half-length ofthe entire length of the moving portion 23. As shown in the right sidedrawing of the FIG. 3A, the lower half part of the moving portion 23 isstored in the cavity portion of the fixing portion 22. The position ofthe lower end 23 a of the moving portion 23 sinks down from the positionillustrated in FIG. 3A.

FIG. 3C shows a prospective view for illustrating the blade 20 c incondition the blade has the shortest length. The moving portion 23 ispositioned at the most retreat position. Namely, the moving portion 23is stored in the cavity portion of the fixing portion 22 and the tip endof the moving portion 23 appears from the upper end 22 a of the fixingportion 22.

FIG. 4A shows a developed view in condition of cutting off a part, forillustrating a connecting portion between the moving portion 23 and thefixing portion 22 of one blade. In addition, FIG. 4B shows a sectionalview along X-X line of FIG. 4A. Incidentally, the thickness of the bladeis magnified in FIG. 4B. The fixing portion 22 comprises a front plate22 d and a rear plate 22 e. The cavity portion 27 is formed between thefront plate 22 d and the rear plate 22 e. In case where the movingportion 23 retreats, the moving portion 23 is stored in the cavityportion 27. The male screw rod 25 extends along the blade axis C3 in thecavity portion 27.

The base end of the male screw rod 25 is rotatably supported on theblade supporting portion 13 (referring to FIG. 3A). The base end of themale screw rod 25 is capable of rotating in every direction by thedriving means such as a motor. The driving means such as a motor iscontrolled in accordance with an output signal of a sensor such as ananemometer which detects a wind speed. As a result, the male screw rod25 is rotated in an appreciate direction by the driving means. In casewhere the wind speed exceeds a tolerance range of the length of theblade, the blade, namely, the windmill is prevented from the damagebased on the wind pressure, by retreating the moving portion 23 toshorten the length of the blade. In addition, the moving portion 23 iscontrolled to project and the length of the blade is lengthened in thetolerance range, in order to enlarge the receiving area of wind in theblade and raise an energy conversion efficiency of the wind.

The moving portion 23 comprises a front plate 23 d and a rear plate 23e. A cavity portion 28 is formed between the front plate 23 d and therear plate 23 e. The female screw plate 26 is fixed in the cavityportion 28 of the moving portion 23. Namely, the moving portion 23 movestogether with the female screw plate 26. Inasmuch as the female screwplate 26 is screwed into the above-mentioned male screw rod 25, thefemale screw plate 26, namely, the moving portion 23 moves along themale screw rod 25, when making the male screw rod 25 rotate. In case ofchanging the rotating direction of the male screw rod 25, the movementdirection varies in the female screw plate 26, namely, the movingportion 23. As described above, variation is carried out as regards theprojection length from the fixing portion 22 in the moving portion 23.

As shown in FIG. 4A and FIG. 4B, rails 23 b is mounted in the appreciatenumber on the outer surfaces of the front plate 23 d and the rear plate23 e of the moving portion 23. The rails 23 b extend along the movementdirection of the moving portion 23. The rails 23 b may be, for example,grooves which are formed on the outer surfaces of the front plate 23 dand the rear plate 23 e of the moving portion 23. Alternatively, therails 23 b may be other members which are mounted on the outer surfacesof the front plate 23 d and the rear plate 23 e of the moving portion23. On the other hand, bearings 22 b are mounted in the appreciatenumber on the fixing portion 22. The bearings 22 b are fitted into therails 23 b. The bearings 22 b are mounted on the inner surfaces thefront plate 22 d and the rear plate 22 e of the fixing portion 22.

When the moving portion 23 retreats after the moving portion 23 projectsfrom the fixing portion 22, the bearings 22 b and the rails 23 b movewith the bearings 22 b being fitted into the rails 23 b, inasmuch as thebearings 22 b are mounted on the fixing portion 22 and inasmuch as therails 23 b mounted on the moving portion 23 are capable of being fittedinto the bearings 22 b. As a result, it is possible to make the movingportion 23 smoothly move.

According the present invention as described above, it is possible toadjust the receiving area of wind on adjusting the length of the bladeby making the moving portion project and retreat from the fixing portionin accordance with the wind speed, inasmuch as the blade comprises thefixing portion supported on the blade supporting portion and extendingto the radial direction, and the moving portion connected to the upperend of the fixing portion, and the moving portion is capable ofprojecting and retreating from the fixing portion to the radialdirection, and the windmill structure further comprises control meansfor changing the projection length of the moving portion in accordancewith the wind speed.

In addition, the fixing portion comprises the front plate and the rearplate and the cavity portion is formed between the front plate and therear plate. The moving portion is stored in the cavity portion of thefixing portion when the moving portion retreats. Inasmuch as each of thefixing portion and the moving portion has the propeller shape having asame twisted degree, it is possible to smoothly store the moving portioninto the fixing portion.

Furthermore, the control means comprises the male screw rod rotatablysupported on the blade supporting portion and extending to the radialdirection in the cavity portion of the fixing portion, the sensor fordetecting the wind speed, driving means for make the male screw rodrotate in accordance with the output of the sensor, and the female screwplate fixed on the moving portion and screwed into the male screw rod.The female screw plate moves along the male screw rod on the basis ofthe rotation of the male screw rod so that the projection length of themoving portion is changed in accordance with the wind speed. By makingthe supported male screw rod rotate, the female screw plate screwed intothe male screw rod moves along the male screw rod. It is possible tomake the female screw plate move to every direction on the basis of therotation direction of the male screw rod. Inasmuch as the female screwplate is fixed to the moving portion, the moving portion moves togetherwith the female screw plate. As a result, it is possible to make themoving portion move to the projection direction and the retreatdirection.

In addition, the windmill structure comprises the bearing mounted on thefixing portion and the rail mounted on the moving portion. The rail isfitted into the bearing. The rail moves with the rail being fitted intothe bearing when the moving portion projects and retreats. The bearingand rail function as a guide for guiding the moving portion when themoving portion projects and retreats. As a result, it is possible tomake the moving portion smoothly project and retreat.

1. A windmill structure for use in a wind power apparatus in which adynamo-electric generator is driven by a main shaft to which a rotationof a windmill is transmitted, said windmill comprising at least oneblade which extends in a radial direction from a blade supportingportion of a main shaft tip in relation to said main shaft, wherein saidwindmill structure comprises: said blade comprising a fixing portionsupported on said blade supporting portion and extending to a radialdirection, and a moving portion connected to an upper end of said fixingportion, said moving portion being capable of projecting and retreatingfrom said fixing portion to the radial direction; and control means forchanging the projection length of said moving portion in accordance witha wind speed.
 2. A windmill structure for use in a wind power apparatusas claimed in claim 1, wherein: said fixing portion comprises a frontplate and a rear plate, a cavity portion being formed between said frontplate and said rear plate; and said moving portion being stored in saidcavity portion of the fixing portion when said moving portion retreats.3. A windmill structure for use in a wind power apparatus as claimed inclaim 1 or 2, wherein: said control means comprises a male screw rodrotatably supported on said blade supporting portion and extending tothe radial direction in said cavity portion of the fixing portion, asensor for detecting the wind speed, driving means for make said malescrew rod rotate in accordance with an output of said sensor, and afemale screw plate fixed on said moving portion and screwed into saidmale screw rod; and said female screw plate moving along said male screwrod on the basis of the rotation of said male screw rod so that theprojection length of said moving portion is changed in accordance withthe wind speed.
 4. A windmill structure for use in a wind powerapparatus as claimed in any one of claims 1 to 3, wherein: said windmillstructure comprises a bearing mounted on said fixing portion and a railmounted on said moving portion, said rail being fitted into saidbearing; and said rail moving with said rail being fitted into saidbearing when said moving portion projects and retreats.